The present invention relates to a method and apparatus for sampling cargo for chemical residues and, more particularly, to a method and apparatus for extracting particulates and vapors of chemical residues simultaneously from multiple cargo items.
Cargo, such as agricultural produce, general merchandise, and passengers' baggage, is routinely checked for chemical residues at transit points such as airports, seaports and border crossings generally. In the case of agricultural produce, the residues sought generally are pesticides and other health hazards. In the case of general merchandise and baggage, the residues sought include illicit substances such as drugs and explosives. This sampling can be tedious and time-consuming. For example, agricultural produce is inspected by selecting a representative sample, mechanically chopping the sample and chemically analyzing the sample. The familiar x-ray inspection of passengers' baggage at airports is performed one item at a time. The quality of this inspection depends on the alertness of the operator to spot suspicious items by their outline against complex backgrounds, as well as on equipment limitations. For a more intensive search based on chemical analysis, chemical samples are collected manually from the outside surfaces, or less commonly from the surfaces of the inside contents, of suspect baggage and parcels and transferred to an analytical instrument or to a reagent chemical test kit for identification. These manual sampling/analysis procedures can detect traces of pesticides on or within agricultural produce, as well as traces of illegal drugs and explosives deposited on the sampled surfaces in the course of handling drugs and explosives and hiding them in the baggage, parcels or cargo, but these procedures generally are slow and tedious, and therefore are restricted to a limited random sample of the inspected items.
A variety of automatic and semiautomatic systems have been proposed for collecting vapors and particulates from cargo items. These generally require that the items be loaded individually into a sampling chamber, although Cohen et al., in U.S. Pat. No. 5,162,652, teach the simultaneous loading of several items into several chambers, albeit still only one item per chamber. The invention of Cohen et al. and also the inventions of Jenkins, described in U.S. Pat. No. 3,941,357, and of Bradshaw et al., described in U.S. Pat. No. 3,998,101, are directed towards extracting vapor from the interior of sealed cargo by varying the pressure within the sampling chamber, typically by up to about 10% on either side of atmospheric pressure. Corrigan et al., in U.S. Pat. No. 5,345,809, and Reid et al., in U.S. Pat. No. 4,580,440, address the problem of sampling particulates on the surfaces of cargo items. Corrigan et al. teach a sampling chamber in which brushes remove particulates from the surfaces of cargo items. Reid et al. teach the agitation of a cargo transport container to suspend, in the air therein, particulates from the surfaces of the cargo items therein, followed by the sampling of the air with the suspended particulates. None of these prior art patents has addressed the problem of sampling particulates contained inside the cargo items.
There is thus a widely recognized need for, and it would be highly advantageous to have, an automatic contaminant sampling method that extracts samples automatically from several inspected items such as cargo items at once, and also extracts particulate contaminants from the interiors of the inspected items.